Enable/Disable Mobile Data (GPRS) using code

Use the following method. It'll work with all android versions.

int bv = Build.VERSION.SDK_INT;

boolean turnOnDataConnection(boolean ON,Context context)
 {

     try{
      if(bv == Build.VERSION_CODES.FROYO)

         {
          Method dataConnSwitchmethod;
            Class<?> telephonyManagerClass;
            Object ITelephonyStub;
            Class<?> ITelephonyClass;

            TelephonyManager telephonyManager = (TelephonyManager) context
                    .getSystemService(Context.TELEPHONY_SERVICE);

            telephonyManagerClass = Class.forName(telephonyManager.getClass().getName());
            Method getITelephonyMethod = telephonyManagerClass.getDeclaredMethod("getITelephony");
            getITelephonyMethod.setAccessible(true);
            ITelephonyStub = getITelephonyMethod.invoke(telephonyManager);
            ITelephonyClass = Class.forName(ITelephonyStub.getClass().getName());

            if (ON) {
                dataConnSwitchmethod = ITelephonyClass
                        .getDeclaredMethod("enableDataConnectivity");
            } else {
                dataConnSwitchmethod = ITelephonyClass
                        .getDeclaredMethod("disableDataConnectivity");   
            }
            dataConnSwitchmethod.setAccessible(true);
            dataConnSwitchmethod.invoke(ITelephonyStub);

           }
         else
           {
             //log.i("App running on Ginger bread+");
             final ConnectivityManager conman = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
             final Class<?> conmanClass = Class.forName(conman.getClass().getName());
             final Field iConnectivityManagerField = conmanClass.getDeclaredField("mService");
             iConnectivityManagerField.setAccessible(true);
             final Object iConnectivityManager = iConnectivityManagerField.get(conman);
             final Class<?> iConnectivityManagerClass =  Class.forName(iConnectivityManager.getClass().getName());
             final Method setMobileDataEnabledMethod = iConnectivityManagerClass.getDeclaredMethod("setMobileDataEnabled", Boolean.TYPE);
             setMobileDataEnabledMethod.setAccessible(true);
             setMobileDataEnabledMethod.invoke(iConnectivityManager, ON);
           }


         return true;
     }catch(Exception e){
                        Log.e(TAG,"error turning on/off data");

                        return false;
                        }

 }

Permissions Required:

<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
<uses-permission android:name="android.permission.UPDATE_DEVICE_STATS"/>
<uses-permission android:name="android.permission.MODIFY_PHONE_STATE"/>
<uses-permission android:name="android.permission.READ_PHONE_STATE"/>

UPDATE:

Starting from Android L this works only for System applications

This code running in android gingerbread and higher:

private void setMobileDataEnabled(Context context, boolean enabled) {
   final ConnectivityManager conman = (ConnectivityManager)  context.getSystemService(Context.CONNECTIVITY_SERVICE);
   final Class conmanClass = Class.forName(conman.getClass().getName());
   final Field iConnectivityManagerField = conmanClass.getDeclaredField("mService");
   iConnectivityManagerField.setAccessible(true);
   final Object iConnectivityManager = iConnectivityManagerField.get(conman);
   final Class iConnectivityManagerClass =  Class.forName(iConnectivityManager.getClass().getName());
   final Method setMobileDataEnabledMethod = iConnectivityManagerClass.getDeclaredMethod("setMobileDataEnabled", Boolean.TYPE);
   setMobileDataEnabledMethod.setAccessible(true);

   setMobileDataEnabledMethod.invoke(iConnectivityManager, enabled);
}

NOTE: U MUST ADD THIS BELOW LINE IN ANDROIDMAINFEST.XML

<uses-permission android:name="android.permission.CHANGE_NETWORK_STATE"/>

You also need that permission:

<uses-permission android:name="android.permission.MODIFY_PHONE_STATE"/>